In general, a fiber optic transceiver is a communications device that transmits and receives fiber optic signals, e.g., through a set of fiber optic cables. Such a device typically secures to a circuit board and electronically conveys data contained within the fiber optic signals to and from electronic circuitry of the circuit board. As a result, the electronic circuitry is capable of performing useful operations, e.g., routing or switching the data, storing the data in a cache or a disk array, etc.
There are a variety of “off-the-shelf” fiber optic transceivers which are available in standardized packages. For example, XENPAK and X2 are standards for pluggable transceiver packages which are optimized for IEEE 802.3ae Ethernet communications. Both the XENPAK standard and the X2 standard are outlined in respective Multi-Source Agreements (MSAs) which are supported by several leading networking component suppliers. As another example, small-form factor (SFF) and small-form factor pluggable (SFP) are standards for transceiver packages which are optimized for high-speed Fibre Channel applications (e.g., 4 Gb/s communications).
In connection with X2, this standard defines a fiber optic transceiver module (hereinafter simply referred to as the X2 module) having a plane-shaped device package and a heat sink which fastens to one side of the device package. The X2 standard further defines a 70-pin electrical connector which mounts to a printed circuit board or PCB (e.g., a front panel, a mid board, a PCI card, etc.), as well as a metallic side rail which attaches to the PCB around three sides of the 70-pin electrical connector with the fourth side of the 70-pin electrical connector remaining exposed. In accordance with the X2 standard, the device package slides within the metallic side rail until a leading edge of the device package electrically connects with the exposed side of the 70-pin electrical connector thus forming a set of electrical connections between circuitry within the X2 module device package and circuitry on the PCB. Such installation is capable of taking place while the 70-pin electrical connector is hot/active/powered, i.e., the X2 module is “hot pluggable” and thus capable of connecting to the 70-pin electrical connector while the PCB is powered up and in operation. At this point, the metallic side rail holds the X2 module firmly in place and operates as an electromagnetic interference (EMI) gasket. Furthermore, the metallic side rail allows unblocked airflow over the full length of the heat sink thus enabling an air stream to provide maximum cooling to the device package and the circuitry contained therein.